Transforming quantum states between reference frames

In the 1970s, Fulling, Davis, and Unruh have shown that a quantum mechanical state must be described differently in different reference frames; otherwise, quantum mechanics would contain contradictions. We present a simple method for transforming any quantum state between the Minkowski and Rindler reference frames. We show that a Wigner-like distribution, commonly used in quantum optics, is useful for treating this problem. To illustrate our method, we transform the Minkowski vacuum and number states into Rindler space, and transform the Rindler vacuum into Minkowski space, as examples. Our method could be generalized to other cases as well.